This invention relates generally to plural component spray systems, and, more particularly, relates to a spray gun which can be easily converted from air atomizing to airless operation which provides external mixing of two components such as catalyst and resin.
In present plural component delivery and sprayin systems, one or more of the components is delivered under high pressure to a nozzle for external mixing with a catalyst. These systems generally use an airless high pressure delivery system which, because of the high pressure, has inherent problems. These high pressure delivery systems also have difficulty in assuring a homogenous mixture, and an incorrect ratio of components can occur because of the very high pressures. Additionally, flushing with an expensive flammable solvent is necessary, because with an internal mixing there is a resin set-up inside the gun from cross-feeding to catalyst passages which could severely damage the gun, or at least render the gun useless until clogged passageways are cleared. After resin set-up, cleaning can be a difficult and time consuming process, if not altogether impossible.
As a solution to the problem, an air atomizing gun was developed, and is disclosed and claimed in U.S. Pat. No. 4,175,702, issued Nov. 27, 1979, to the same assignee as the present invention. In the spray gun disclosed and claimed in this patent, a nozzle gun body having an air delivery passageway, delivers air to a chamber adjacent the outlet to the nozzle for spraying one of the components. In this chamber, the component is atomized by turbulence created in the air flow, providing an air atomized or nucleating system for delivering resin and air, or atomized resin to the fluid tip for external mixing with catalyst.